/Engine/Source/Runtime/SlateCore/Public/Layout/Children.h
Removes the corresponding widget from the set of children if it exists. Returns the index it found the child at, INDEX_NONE otherwise.
int32 Remove ( const [TSharedRef](API\Runtime\Core\Templates\TSharedRef)< [SWidget](API\Runtime\SlateCore\Widgets\SWidget) > & SlotWidget )